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{One-Bowl, Big-Batch} Monster Cookie Bars

Loaded with oats, peanut butter, and M&M’s, these chewy Monster Cookie Bars require only one bowl yet yield a BIG batch, making this the perfect easy recipe when you need a bunch of sweet treats for a party or celebration!

Mid-January each year is when I find myself feeling torn as a food blogger. Do I continue sharing healthy, wholesome recipes in line with everyone’s New Year’s resolutions? Or do I look ahead to Superbowl and Valentine’s Day and start sharing cheesy dips and yummy appetizers and chocolate-laden sweets? Well, as you can probably surmise by the above mouthwatering Monster Cookie Bars collage, the latter option won me over today. Forgive me, resolution-keepers? 😉

You’ve all heard of Monster Cookies, right? They’re known for being nice and chewy thanks to rolled oats, they have an unmistakable (and yummy) undertone of peanut butter, and this version is loaded with not one, not two, but THREE different confections: M&Ms, chocolate chips, and peanut butter chips! Seriously, this is a recipe that you definitely want in your arsenal. But why do I love it so? Let me count the ways.

First of all, the M&Ms in these bars make them fun to customize for various holidays. Add them in the colors of your favorite team for the upcoming Superbowl. Pick up a bag of Valentine M&Ms for red, pink, and white-studded treats. Use Reese’s Pieces in place of M&Ms for pretty fall colors, or buy seasonal M&Ms in color schemes from Halloween to Christmas to Easter to the 4th of July for festive, holiday-themed cookie munching all year long!

Next, this recipe is super quick and easy to whip up. The dough comes together really quickly — there’s not even any flour to measure out! — and in the process of making them, you only end up dirtying a few measuring cups/spoons and just one bowl.

Furthermore, these bars are baked in a large sheet pan that results in a ton of bars, meaning that this recipe is perfect when you need a large quantity of treats in one easy batch. Now to back up just a bit, I’m notorious for turning classic cookies into bar cookies…because when I need to bring a baked treat to an event, I’ve found that it’s way faster to spread batter in a pan and bake as opposed to hand-forming dozens of individual cookies. So I took my classic Monster Cookie recipe and did just that…baked the batter in a 9- by 13-inch baking pan. Unfortunately, my bars turned out pretty thick, which resulted in them being a bit too underdone in the center and a bit too overdone around the edges of the pan (not that we didn’t happily eat the rejects, mind you).

Anyway, I decided to scrap that approach, tweak my ingredient amounts, and try, try again, this time taking a hint from my favorite brownie recipe and making these bars in a large, rimmed half sheet pan for more even baking. And ding, ding, ding…it worked! The cookies were perfectly soft and chewy without being too gooey in the middle or too crunchy around the edges. In other words, Monster Cookie Bar perfection!

(Just be sure that you’re aware of any potential peanut allergies before sharing these treats at a party or celebration…it may not be obvious to everyone that they contain peanut butter.)

But my final (and probably most important) reason for loving these Monster Cookie Bars is that they are freaking delicious. The chewy texture, the variety of goodies within, and the peanut butter goodness make for one tasty treat.

So the next time you need a large, effortless batch of cookies for sharing, look no further than these Monster Cookie Bars! They’re colorful, they’re fun, they’re totally addictive…and I promise that your big ol’ cookie sheet will be empty in no time. 😉

{One-Bowl, Big-Batch} Monster Cookie Bar Recipe

{One-Bowl, Big-Batch} Monster Cookie Bars

Yield: 24 to 36 bars, depending on size

Loaded with oats, peanut butter, chocolate & PB chips, and M&M's, these chewy Monster Cookie Bars require only one bowl yet yield a BIG batch, making this the perfect easy recipe when you need a bunch of sweet treats for a party or celebration!

Ingredients

4 eggs

1 1/2 cups sugar

1 cup brown sugar

3/4 teaspoon salt

1 tablespoon pure vanilla extract

16-ounce jar (2 cups) peanut butter (creamy or crunchy)

5 tablespoons butter, at room temperature

2 1/2 teaspoons baking soda

18-ounce container (5 cups) old-fashioned oats

1 cup M&Ms

1/2 cup semisweet chocolate chips

1/2 cup peanut butter chips

Instructions

Position rack in center of oven and preheat to 350°F. Generously butter a 18x13x1-inch rimmed half sheet pan. Set aside.

In a very large bowl (using a spoon or electric mixer), mix together the eggs and sugars until well-combined. Beat in the salt, vanilla, peanut butter, and butter until smooth. Stir in the baking soda (make sure there aren't any lumps) and the oats, then add the M&Ms, chocolate chips, and peanut butter chips and mix until just combined.

Spread the batter into the prepared baking pan, pressing down and smoothing the top into an even layer. Bake for 18 to 22 minutes or until edges are very light golden brown and center is set. Allow to cool in the baking pan before slicing and serving.

5.0.12

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Comments

Wow! First time making monster anything and I was hesitant with this recipe because it didn’t have any flour. Boy was I wrong!!!! So delicious & chewy. This recipe is now my families favorite cookie recipe. Thanks for sharing.

Awesome recipe! I substituted Wow! Butter for the peanut butter so my class can make these at our nut free school and they turned out fabulous! So no gluten and no peanut butter, but an amazing bar! Thank you!!

I rarely do this, but I have to say – REALLY excellent cookie bar. I like Monster Cookies. My kids don’t eat oatmeal. We are fighting over these things – hiding them from each other. The kids really liked them, and I love them. We will totally be making these again so the kids can take them to lunch at school. Thank you for a quick, easy and delicious cookie that I feel better about making for them. Actually, my son made these, so it’s even less work for me!

Hi Tracy! Sorry to hear that. My first guess would be that perhaps you didn’t bake your bars in a true half sheet pan measuring 18x13x1″? Using a smaller pan would result in thicker bars that may not cook through in the center. If you used the correct size pan, the edges do become a little firmer than the center, but overall, the bars should have cooked pretty evenly.

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Hi, I’m Samantha . . .

a busy wife and tired mama of two energetic boys and a sweet little girl living in Texas. I love cooking, writing, eating queso, watching college football, and taking way too many pics of my kids. In my “spare” time, I run this food blog and I wrote a cookbook. The days are crazy but the love is plenty between the five hearts that make up our home! (click for more)